A microfiche appendix, Appendix A, is included of a computer program listing. The total number of microfiche is 6. The total number of frames is 186. A second microfiche appendix, Appendix B, is also included of schematic diagrams. The total number of microfiche is 1 and the total number of frames is 23.
A portion of the disclosure of this patent document contains material which is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure, as it appears in the Patent and Trademark Office patent file or records, but otherwise reserves all copyright rights whatsoever.
This invention relates to revenue meters of the type used by energy suppliers to accurately measure electrical energy delivered to consumers for the purposes of billing and/or collecting revenue and more particularly, this invention relates to revenue meters having power quality monitoring, detection, quantification and reporting capabilities.
In a typical electrical distribution system, electrical energy is generated by an electrical supplier or utility company and distributed to consumers via a power distribution network. The power distribution network is the network of electrical distribution wires which link the electrical supplier to its consumers. Typically, electricity from a utility is fed from a primary substation over a distribution cable to several local substations. At the substations, the supply is transformed by distribution transformers from a relatively high voltage on the distributor cable to a lower voltage at which it is supplied to the end consumer. From the substations, the power is provided to industrial users over a distributed power network that supplies power to various loads. Such loads may include, for example, various power machines.
At the consumer""s facility, there will typically be an electrical energy meter (xe2x80x9crevenue meterxe2x80x9d) connected between the consumer and the power distribution network so as to measure the consumer""s electrical demand. The revenue meter is an electrical energy measurement device which accurately measures the amount of electrical energy flowing to the consumer from the supplier. The amount of electrical energy measured by the meter is then used to determine the amount for which the energy supplier should be compensated.
Typically, the electrical energy is delivered to consumers as an alternating current (xe2x80x9cACxe2x80x9d) voltage that approximates a sine wave over a time period. The term xe2x80x9calternating waveformxe2x80x9d generally describes any symmetrical waveform, including square, sawtooth, triangular, and sinusoidal waves, whose polarity varies regularly with time. The term xe2x80x9cACxe2x80x9d (i.e., alternating current), however, almost always means that the current is produced from the application of a sinusoidal voltage, i.e., AC voltage. The expected frequency of the AC voltage, e.g., 50 Hertz (xe2x80x9cHzxe2x80x9d), 60 Hz, or 400 Hz, is usually referred to as the xe2x80x9cfundamentalxe2x80x9d frequency. Integer multiples of this fundamental frequency are usually referred to as harmonic frequencies.
While the fundamental frequency is the frequency that the electrical energy is expected to arrive with, various distribution system and environmental factors can distort the fundamental frequency, i.e., harmonic distortion, can cause spikes, surges, or sags, and can cause blackouts, brownouts, or other distribution system problems. These problems can greatly affect the quality of power received by the power consumer at its facility or residence as well as make accurate determination of the actual energy delivered to the consumer very difficult.
In order to solve these problems, revenue meters have been developed to provide improved techniques for accurately measuring the amount of power used by the consumer so that the consumer is charged an appropriate amount and so that the utility company receives appropriate compensation for the power delivered and used by the consumer. Examples of such metering systems are well known in the art.
While these conventional revenue accuracy type metering systems provide information about the quality of the power, i.e., frequency and duration of blackouts, brownouts, harmonic distortions, surges, sags, swells, imbalances, huntings, chronic overvoltages, spikes, transients, line noise, or the like, received by a power consumer at a particular consumer site, they fail to monitor and quantify the power quality with a sufficient level of detail. Blackouts, brownouts, harmonic distortions, surges, sags, swells, imbalances, huntings, chronic overvoltages, spikes, transients and line noise are all examples of power quality events. As utility companies become more and more deregulated, these companies will likely be competing more aggressively for various consumers, particularly heavy power users, and the quality of the power received by the power consumer is likely to be important. This, in turn, means that accurate and detailed reporting and quantification of power quality events and overall power quality will become more and more important as well.
For example, one competitive advantage that some utility companies may have over their competitors could be a higher quality of the power supplied to and received by the consumer during certain time periods. One company may promote the fact that it has fewer times during a month that power surges reached the consumer causing potential damage to computer systems or the like at the consumer site. Another company may promote that it has fewer times during a month when the voltage level delivered to the consumer was not within predetermined ranges which may be detrimental to electromagnetic devices such as motors or relays. Previous revenue accuracy meters which provide for measuring quality of power in general lack the necessary accuracy and features to provide the consumer and the power utility with the needed information.
Accordingly, there is a need for a revenue accuracy meter that is capable of monitoring, reporting and quantifying the quality of power with a high level of detail and accuracy. Further there is a need for a revenue accuracy meter that can continue to monitor and quantify data throughout the duration of a power quality event and prevent loss of recorded power quality information in the event of a catastrophic power quality event such as a complete power failure.
By way of introduction, the preferred embodiments described below relate to revenue accuracy electrical power metering devices with the ability to detect, monitor, report, quantify and communicate power quality information about the power which they are metering. More particularly, the preferred embodiments relate to revenue accuracy electrical metering devices having the capabilities of power quality event xe2x80x9cride thruxe2x80x9d, transient detection, wave shape quantification, sag/swell detection, harmonic content quantification, symmetrical component quantification, waveform recording and direct memory access data transfer. These capabilities provide a revenue accuracy meter which can continue to monitor and quantify data throughout the duration of a power quality event and prevent loss of recorded power quality information in the event of a catastrophic power quality event such as a complete power failure.